Thomas -
We test the spring water regularly and it is safe to drink. The spring flows year round and has for centuries. We carbon dated the water to about 1360 CE but will need to do the same with other sources to positively identify the aquifer.
I've made several trips down the Trinity by canoe and kayak - no sweat and no smell.
Everything you need to know about the Great Trinity Forest is right here: http://dallastrinitytrails.blogspot.com/
I'm camping on private property but the spring itself is now owned by the City of Dallas. We are in the process of defining Historic Landmark and Conservation Easement overlays. The spring is adjacent to the Texas Horse Park currently under construction and not publicly accessible at present.
Future plans in the vicinity will include an RV Park and Canoe Launch Site in the old Roosevelt Heights Addition near US 175 and Bruton Road. In the meanwhile there are a number of established trails and trailheads where you can access the Forest on foot, bike or horseback. There is also the Trinity River Audubon Center. http://trinityriver.audubon.org/